Exotic ground states and impurities in multiband superconductors

TL;DR

This paper investigates how isotropic impurities affect exotic multiband superconducting states in cubic and hexagonal materials, revealing a weaker suppression of non s-wave states than expected for unconventional superconductors.

Contribution

It provides a detailed analysis of impurity effects on multiband superconductors with complex Fermi surfaces, highlighting a weaker suppression of unconventional states.

Findings

Non-magnetic impurities weakly suppress exotic superconducting states

Superconducting states in studied materials are more robust than typical unconventional superconductors

Impurity effects depend on Fermi surface topology and symmetry considerations

Abstract

We consider the effect of isotropic impurity scattering on the exotic superconducting states that arise from the usual BCS mechanism in substances of cubic and hexagonal symmetry where the Fermi surface contains inequivalent but degenerate pockets (e.g. around several points of high symmetry). As examples we look at CeCo$_2$, CeRu$_2$, and LaB$_6$; all of which have such Fermi surface topologies and the former exhibits unconventional superconducting behavior. We find that while these non s-wave states are suppressed by non-magnetic impurities, the suppression is much weaker than would be expected for unconventional superconductors with isotropic non-magnetic impurity scattering.